Previously, many types of drives and different configured wheelchairs have been in use to provide an effective means of self-propulsion by disabled persons. The conventional type of wheelchair employed today utilizes an extended rim or rail protruding from each fixed wheel allowing the user to grasp the rim and propel the chair by moving the wheel directly by hand grasping small segments at a time. Conversely, many types of hand cranks have been employed using manual energy transmitted to the wheels generally by chains. Others have developed mechanisms that provide hand operated wheels driving the wheelchairs fixed support wheels, again, by chains. Still, others have employed levers with gears, ratchets, clutches, etc., in an attempt to transmit human energy from upper body limbs to drive wheelchairs.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however, the following U.S. patents were considered related:
______________________________________ U.S. Pat. No. Inventor Filing Date ______________________________________ 4,762,332 Seol Aug. 9, 1988 4,758,013 Agrillo Jul. 19, 1988 4,732,402 Lambert Mar. 22, 1988 4,682,784 Anderson Jul. 28, 1987 4,560,181 Herron Dec. 24, 1985 4,274,651 Dumont Jun. 23, 1981 4,044,850 Winsor Aug. 30, 1977 3,442,532 Gardener et al May 6, 1969 2,946,602 Lee Jul. 26, 1960 2,452,886 Wood Nov. 2, 1948 ______________________________________
Agrillo teaches a hand crank powered wheelchair with forward, coast, reverse, and braking capability. Each hand crank is independent of the other. A clutch and brake are disposed in the hub of each rear wheel. A reverse lever selects the brake of reverse mode of operation. A crank arm transmits the rotational power via a drive chain with a drive sprocket having a handle and a driven sprocket integral with the coaster brake. In another embodiment a driveshaft and beveled gears are employed to transmit the rotational power.
Lambert utilizes a hand wheel attached by a chain transmission to a driving wheel with the chair back and leg supports in the conventional position. The hand wheels are substantially larger than the drive wheels, allowing the disabled person to move the wheelchair with the least possible effort. This arrangement and use of the hand wheel allows the wheelchair to be propelled on wet or dirty ground without soiling the persons hands or clothing.
Dumont, on the other hand, employs a similar mechanical drive using a flexible chain drive and a rotatable hand crank. The drive includes a clutch assembly that is responsive to the cam drivingly connecting the hand crank to the main wheel. The clutch is engaged by moving a handle to a drive position, thus cammingly engaging the clutch, thereby driving the wheel. Further, a neutral position permits the drive wheel to coast conserving the operators energy when not required.
Gardner et al is concerned with improvements in the foldability and portability of a wheelchair along with a chain driven propulsion system that does not require the user to exert excessive force in negotiating normal inclines using a continuous chain between relatively small sprockets.
Wood employs a hand crank to drive one wheel and a steering handle on an opposite wheel. The hand crank is directly connected to a sprocket wheel and the chain drives a similiar but larger sprocket wheel secured to the hub of the right rear wheel. The embodiment is so arranged as to allow construction of wood.
For background purposes and as indicative of the art to which the invention relates reference may be made to the remaining cited patents, most of which employ a lever controlled mechanism manipulated by the operator for propulsion of the wheelchair.